1. Field of the Invention
The present invention relates to improvements in an image stabilizing apparatus for preventing an image from blurring due to the movement of hands or the like.
2. Related Background Art
Hitherto, there was known an optical apparatus having a function for preventing a picture image from blurring due to hand movement or the like. For example, an apparatus in which a compensatory optical system is movably disposed and picture images are prevented from blurring by the inertia thereof is disclosed in U.S. Pat. Nos. 2,959,088 and 2,829,557.
FIG. 19 shows the entire construction of an image stabilizing apparatus of such a type. In FIG. 19, lenses 1 and 2 constitute the compensatory optical system for compensating blurring of images formed on a focal plane 14 through main lenses 12 and 13 fixed to a lens barrel 4 (hereinafter referred to simply as a barrel). If the focal length of the lens 1 (fixed to the barrel 4 and with a negative power) is denoted as f.sub.1 ; and that of the lens 2 (supported on a movable support member 3 and with a positive power) is denoted as f.sub.2, then the focal length of the compensatory optical system is set in such a manner as to satisfy the following relationship: f.sub.1 =-f.sub.2.
The movable support member 3 is supported on the barrel 4 by means of a gimbal 5 for supporting two-shaft movement at a position of the focal length f.sub.2 (=-f.sub.1) from the principal point on the image size of the lens 2.
FIG. 20 shows the construction in which the gimbal 5 is supported so as to be biaxially movable. The movable support member 3 for supporting the lens 2 is supported on a support member 5y having a freedom about the y axis; the support member 5y is supported on a support member 5x having a freedom about the x axis which is perpendicular to the y axis; and the support member 5x is supported on the barrel 4. Thus, a compensatory optical system having two shafts freely rotatable is constructed.
In FIG. 19, reference numeral 10 denotes a counter weight employed as a balancer for balancing the movable support member 3. The counter weight 10 is mounted on the movable support member 3 towards the end opposite to the lens 2 with the gimbal 5 being grasped therebetween, so that the gimbal 5 balances with the lens 2.
The above construction will realize a stabilization optical system of a so-called inertia pendulum optical system. That is, according to the construction of FIG. 19, image blurring can be prevented as described below.
For example, assuming that the construction shown in FIG. 19 is a telescope, an optical image of an object is formed inside the barrel 4 directed to an object on the focal plane 14 by means of the main lenses 12 and 13, and the compensatory optical systems 1 and 2. In a telescope with high magnifying power, vibrations having frequency components in the range of approximately 0.1 to 10 Hz occur in the barrel 4 due to, in particular, the vibration of a hand or the like when the telescope is held by hand. These vibrations cause image blurs.
However, with this vibration in the above-mentioned optical mechanism, a relative displacement occurs between the lens 2 and the lens 1 due to the inertia of the movable support member 3, thus suppressing the above-mentioned image blurring.
In FIG. 19, a member 9 mounted on the movable support member 3 is a non-magnetic conductor, such as an aluminum piece or the like. The magnetic effect formed by magnets 6 and 7 fixed to the barrel 4 produces a damping force on the basis of the vibration speed of the barrel 4. This is for the purpose of producing a damping action for preventing the movable support member 3 from striking the inner wall of the barrel 4, for example, when the barrel 4 is abruptly displaced in order to change the scene viewed.
Specifically, a damping effect is obtained by producing a force in a direction in which the eddy current generated by the conductor 9 makes the amount of the displacement of the movable support member 3 from the movable central position at which the optical axis of the lens 2 coincide with the optical axis (a main optical axis 15) of the main lenses 12 and 13.
In FIG. 21, the magnets 6 and 7 are mounted only on the upper section of the barrel 4. This is an omission for purpose of convenience only. Needless to say, similar magnets are disposed on the lower section, on the right and left of the barrel 4, for effectuating biaxial control.
In FIG. 19, reference numeral 11 denotes a magnetic substance integrally mounted along with the counter weight 10 on the movable support member 3. The magnetic substance performs a centering operation for returning the movable support member 3 to the central position of the movement at which the optical axis of the lens 2 coincides with the main optical axis 15 due to the magnetic effect formed between the magnetic substance and a magnet 8 fixed to the barrel 4. This centering operation is performed to make the optical axis of the lens 2 coincide with the main optical axis 15 by removing the displacement corresponding to the components of the direct current by using manufacturing errors and the frequency components of the above displacement. As a result, excellent optical characteristics can be obtained if the central section of the lens 2 is used when there is no blurring.
To be specific, as is shown in the enlarged view of the magnet 8 in FIG. 21, the same magnetic poles (both are N poles) of the magnetic substance 11 and the magnet 8 face each other so as to magnetically repulse each other. The center of the magnet 8 coincides with the main optical axis 15, with the result that the centering force is generated to make the optical axis of the lens 2 coincide with the main optical axis 15. With a damping and centering arrangement as described above, stabilization characteristics can be improved.
In the above-mentioned apparatus, the compensatory optical system (the movable support member 3) is very easy to move relative to the barrel 4. For this reason, if a large impact is applied to the apparatus while the apparatus (or equipment in which the apparatus is incorporated) is being transported, the movable support member 3 will violently strike the barrel 4 and be deformed. Hence, the stabilization characteristics deteriorate.
As a measure for preventing this deterioration, when the apparatus is not in use, generally, the state of the mechanical fixing means is changed by using a motor or the like and the movable support member 3 is fixed at the central position of the movement.
However, when the fixation of the movable support member 3 by means of the fixing means is released while the apparatus is held, for example, in a state in which the amount of the displacement of the movable support member 3 becomes very large, the movable support member 3 sometimes greatly deviates and strikes the barrel 4. Also, in a case where the state of the fixing means is abruptly changed in order to fix the movable support member 3 when the amount of the displacement of the movable support member 3 in a non-fixed state is large, an excessive force is applied to a driving means for driving the fixing means. This presents the problem that damage or deformation is caused to these components. As a result, another problem arises in that a picture image which is distorted and of poor quality is produced.